Electric relay apparatus



March 31, 1931.

K; LANDSMANN ELECTRIC RELAY APPARATUS Fil ed Aug. 1a, 1926 Patented Mar. 31, 1931 Umran STATES PATENT oFFICE KURT LANDSMANN, OF MANNI-IEIM, GERMANY, ASSIGNOR T AKTIENGESELLSCHAFT BROWN BOVERI & CIE, 0F BADEN, SNITZERLAND, A JOINT-STOCK COMPANY OF SWITZERLAND ELECTRIC RELAY APPARATUS Application filed August 18, 1926, Serial No. 129,975, and in Germany September 3, 1925.

This invention relates generally to relay apparatus, and particularly to apparatus designed for protection of networks or portions thereof or connected lnstallations, against abnormal voltage or current conditions.

current or voltage effects.

Another object is the provision of an arrangement whereby relay apparatus deslgned for carrying relatively low current quantities may be installed in systems normally carrying or subject to much higher current conditions.

A particular object of the invention is the provision of a construction wherein either or both of the advantages indicated above may be attained by comparatively simple and completely reliable means. A

Other and further objects will be pointed out or indicated hereinafter, or apparent to one skilled in the art upon an understanding of the invention.

In the drawing forming a part of this specification I illustrate in diagrammatic fashion certain arrangements of apparatus in which the invention may be embodied, but these are presented for purpose of illustration only and are not to be construed as imposing on the claims any limitations not necessitated by the prior art.

In the drawing, a a

Fig. 1 is a diagram illustrating a relay connection for the operation of a tripping device intended to be brought into operation upon the current in the supply lines or network reaching a predetermined quantlty;

Fig. 2 is a diagrammatic illustration of an arrangement wherein the tripping relay 1s of the no-volttype; and

Fig. 8 is a diagrammatic illustration of an arrangement of a type wherein the winding of the tripping magnet is of the auto-transformer type.

In types of protective apparatus quite generally employed, an electro-magnet is employed for operation of a switch which will isolate the apparatus'to be protected, such detecting relay operating, upon the occurrence of that condition, to bring the tripping relay into operation. It is a matter of convenience and economy to operate both the tripping and detecting relays from the same supply source.

age values'which they can handle without damage or without deterioration of contacts, and with which they can operatewith certainty and reliability. Upon the occurrence ofvarious disturbances such as short-circuits, however, the current may rise to many times the value for which therelays are designed, and the provision of suitable contacts for handling such high currents in the apparatus, or the provision oftransforiners for reducing the current effects, present various difiiculties and involve undesirable complications and increased cost. By virtue of the present invention I am enabled to energize the relaysfrom the system inwhich the ef fects occur without subjecting them to injurious current or voltage influences and Both, however, must have certain limitations as to the current and volt- V the reference numeral 10 designates the lines of the system, in this instance an alternating current system, and 11 designates the transformer for the protective apparatus. The trippingcoil is designated 12, and when energized to a predetermined degree is intended-to operate or initiate operation of the switch opening device. The tripping coil is included in the secondary circuit of the transformer 11, in'which is also connected the coil 14 of the contac'tor or detecting relay, having a movable contact member 146*. The trip ping magnet has woundon the same core with the coil 12, a secondary winding 15 which forms part of a secondary. circuit normally closed by the contact member H Un der normal line conditions, the reduced current from the secondary of the transformer 11 flows through the coil 12 of the tripping magnet, but its magnetizing efi'ect is counteracted by the short-circuited compensating secondary winding 15. Thus the current passing through the contacts of the detecting or overload relay is not the same as that passing through the coils 12 and 14, and through the arrangement of the coils 12 and 15 may be held at such a low value as to preclude injurious efiects on the contacts. The control spring 14 of the overload relay is set, of course, to hold the secondary circuit closed until the power of the relay magnet reaches a predetermined value. When this value is exceeded, however, as occurs upon an overload on the'lines 10, the relay contacts will be opened, and the neutralizing effect of the secondary coil 15 on the tripping magnet will be eliminated, whereupon the tripping magnet will be'energized and operate the tripping mechanism.

Wherever overload relays are employed they are nearly always of the time-limit type, but are nevertheless frequently designed to trip instantaneously in the event of a heavy overload. With the present type of apparatus, this condition may be fulfilled in a very simple manner by suitably designing the windings or c1rcu1ts of the tripping magnet.

. The current induced in the secondary winding 15 cannot completely neutralize the magnetizing effect of the primary current in coil 12, but reduces it to a fraction of its value. If the primary current in coil 12 is increased, this excess or unneutralized magnetization also increases until, at a certain value of the primary current, it is sufficient to operate the tripping mechanism. By suitably choosing the number of turns on the two windings, and by the insertion of resistances, choke coils, or similar simple devices, it is possible to set the current value, above which the tripping mechanism operates instantaneously withoutpreliminary opening of the contact 14, at

any desired quantity to meet the conditions in hand.

In the arrangement illustrated in Fig.2,

, the tripping magnet is a no-volt magnet having the primary winding 16 and the secondary winding 17, the former being connected across the lines 10 and the latter being included in a circuit which may be closed by the movable contactor 18 of the detecting or overload relay 18, the coilof the latter being energized from the line through the transformer 19. The contactor 18 is normally held open by its spring. As the cur rent taken by the no-volt magnet is very small when the secondary circuit is open, and increases greatly when the secondary is closed, it follows that the magnetization of the iron core will vary to a much less extent than is the case with the arrangement shown in Fig. 1. Under some circumstances the closing of the secondary circuit might cause such a rise of current that the winding would be" overloaded. Accordingly, it is advisable to insert an ohmic or inductive resistance 20 in series with the primary winding 16, so that the variation ofthe primary current on opening and closing of the secondary circuit is kept within desirably narrow limits. An appropriate type of resistance for this purpose is one having a high temperature coefficient which varies in resistance in accordance with the current in such a way that the latter remains practically constant within certain limits. In this arrangement the occurrence of an overload on the line causes the overload relay 18 to be energized to a degree overcoming the contactor spring and closing the contacts of the secondary circuit. Upon this occurrence the current in the primary 16 will increase to the point at which the tripping mechanism is operated. This operation andthe subsequent opening of the contactor 18 is accomplished without subjecting the contacts to heavy current.

In the arrangement illustrated in Fig. 3 the winding 21 of the tripping magnet is arranged as an auto-transformer, one pole of the secondary of the transformer 22 being connected at the neutral point of the winding and the opposite ends of the latter normally being connected to the other pole of the transformer secondary. The connection of the lower'end of winding 21 is by way of the movable contactor 24 of the overload relay 24 so that, so long as the current in'the winding of the overload relay is below the critical point, the halves of the auto-transformer winding 21 neutralize each other. Upon the appearance of an overload, however, the neutralizing lower half of the autotransformer winding is cut out by the opening of contactor 24", rendering the still active portion of the winding 21 effective to induce the necessary magnetization of the tripping magnet and operate the tripping mechanism.

WVhat I claim is:

1. In electric relay apparatus, tripping and overload relays each having an operating winding, said overload relay including a switch and spring means normally holding the same in closed position, a transformer having a secondary winding, said relay-opcrating and secondary windings beingconnected in series with respect to each other to constitute a closed circuit, and a winding associated with the operating winding of said tripping relay and connected across said switch to constitute a second closed circuit.

2. In a protective relay system, a switch arranged in a circuit to be protected, a tripping relay having an operating winding, said relay being operableto trip said switch, a detecting relay having an operating Winding energized only upon overload in the circuit to be protected, a transformer connected into the circuit to'be protected, said transformer having a secondary winding connected in series with the operating winding of said relays, and a compensating winding arranged in inductive relation with the operating winding ofsaid tripping relay, the current flow in said compensating winding being controlled by operation of said detecting relay.

3. In a protecting relay system, a switch arranged in a circuit to be protected, a tripping relay having an operating winding, said relay being operable to trip said switch, a detecting relay having an operating winding operable only upon overload in the circuit to be protected, a switch controlled by operation of said detecting relay, a transformer connected into the circuit to be protected, said transformer having a secondary winding connected in series with the operating windings of said relays, and a compensating winding arranged in inductive relation with the operating winding of said tripping relay, said compensating winding and said switch connected therewith forming a closed circuit.

In testimony whereof I have hereunto subscribed m name this 24th day of July, A. D. 1926, at tuttgart, Germany.

0 KURT LANDSMANN. 

